Adsorption of Helium on Small Cationic PAHs: Influence of Hydrocarbon Structure on the Microsolvation Pattern

Arne Schiller (1) , Miriam Meyer (1) , Paul Martini (1) , Fabio Zappa (1) , Serge Krasnokutski (2) , Florent Calvo (3) , Paul Scheier (1)

1 Universität Innsbruck [Innsbruck]
2 Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany]
3 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

The adsorption of up to ∼ 100 helium atoms on the planar polycyclic aromatic hydrocarbons (PAHs) anthracene, phenanthrene, fluoranthene and pyrene in cationic form was studied by combining helium nanodroplet mass spectrometry with classical and quantum computational methods. Recorded time-of-flight mass spectra reveal a unique set of structural features in the ion abundance as a function of the number of attached helium atoms for each of the investigated PAHs. Path-integral molecular dynamics simulations were used with a polarizable potential to determine the underlying adsorption patterns of helium around the PAH cations and in good general agreement with the experimental data. The calculated structures of the helium-PAH complexes indicate that the arrangement of adsorbed helium atoms is highly sensitive towards the structure of the solvated PAH cation. Closures of the first solvation shell around the studied PAH cations are suggested to lie between 29 and 37 adsorbed helium atoms depending on the specific PAH cation. Helium atoms are found to preferentially adsorb on these PAHs following the √ 3 × √ 3 commensurate pattern common for graphitic surfaces, in contrast to larger carbonaceous molecules like corannulene, coronene and fullerenes that exhibit a 1 × 1 commensurate phase.

Domaines: Chimie théorique et/ou physique

Arne Schiller, Miriam Meyer, Paul Martini, Fabio Zappa, Serge Krasnokutski, et al.. Adsorption of Helium on Small Cationic PAHs: Influence of Hydrocarbon Structure on the Microsolvation Pattern. Journal of Physical Chemistry A, 2021, 125 (36), pp.7813-7824. ⟨10.1021/acs.jpca.1c05150⟩. ⟨hal-03854415⟩